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Sapropterin for treating phenylketonuria

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1 Recommendations

1.1 Sapropterin is recommended as an option for treating hyperphenylalaninaemia that responds to sapropterin in people with phenylketonuria (PKU), only if:

  • they are under 18

  • a dose of up to 10 mg/kg is used

  • the company provides it according to the commercial arrangement (see section 2).

1.2 This recommendation is not intended to affect treatment with sapropterin that was started in the NHS before this guidance was published. People having treatment outside this recommendation may continue without change to the funding arrangements in place for them before this guidance was published, until they and their NHS clinician consider it appropriate to stop.

Why the committee made these recommendations

PKU is an inherited condition that causes raised levels of phenylalanine in the blood. Without treatment, this causes irreversible brain damage in babies and children and affects brain function in adults. The only treatment for PKU is a diet to manage phenylalanine and overall protein intake (protein-restricted diet). Sapropterin is used alongside this diet. The aim of treatment is to reduce blood phenylalanine levels and allow a less restricted diet.

Clinical trial evidence compares sapropterin alongside a protein-restricted diet with diet alone. It shows that sapropterin effectively reduces blood phenylalanine levels in people with PKU. It is uncertain how well it works because there is only short-term clinical trial evidence. There is no clinical trial or registry evidence to show whether sapropterin reduces the need for a protein-restricted diet or how it affects quality of life.

The dose of sapropterin is based on weight so costs are higher for adults than children but there is no extra increase in quality of life for adults to offset these costs. There is also no risk of irreversible brain damage in adults with PKU. This means the cost-effectiveness estimates are higher than what NICE considers an acceptable use of NHS resources. Also, there is not enough evidence on how sapropterin might be used to prevent harm to the unborn child in women with PKU who are pregnant or trying to conceive. So, sapropterin is not recommended for adults.

When taking into account the clinical evidence and benefits that were not captured in the cost-effectiveness estimates for children, sapropterin is considered an appropriate use of NHS resources. So, it is recommended for treating PKU in children at a dose of up to 10 mg/kg.